Update/remove uses of Wikidata

Extension was renamed a while ago from Wikidata to WikiLexicalData. To
avoid confusion with the Wikidata project of Wikimedia, I changed some
uses form Wikidata to WikiLexicalDatal. Also removed the "Wikidata: "
prefix for extension related special pages. That's not really needed.
Consider adding all these pages to the same special page group if it's
relevant to make them stand out on Special:SpecialPages.

Inspired by a comment by Purodha Blissenbach at
https://translatewiki.net/wiki/Thread:Support/About_MediaWiki:Ow_db_consistency_not_found/en

Change-Id: Ib69d7125bce732fd24b8f96569fde9282797fac2